In a computer system configured with disk array system and other system such as host computer and others telecommunicated to the disk array system included, a transmission rate of network that connects between systems is more and more increased. To respond to this increase, in a controller of conventional disk array system, a channel adapter of a configuration to control one port unit by multiple processors (host processor units). In communication between host computer and other system and a channel adapter via network under this configuration, a port unit receives commands (data access request) related to data input/output from other system and data transfer processing to meet the received command is carried out by the processor. The data transfer processing in such event is carried out by any of the plural processors which have a channel adapter inside. Examples of the data transfer processing include processing to transfer read data from HDD to other system side in data read processing that supports the read command, processing to transfer write data from the other system side to HDD in data write processing that supports the write command, and others. In the data transfer processing, typically, the read/write data is temporarily cached by the memory held in the controller.
In the technique described in Japanese Patent Application Laid-Open Publication No. 2001-318904, a method for distributing data access task between a large number of storage unit controllers or a large number of processors is provided.